1. Field of the Invention
This invention generally relates to hand trucks or dollies and the wheels thereof. More specifically, this invention is directed to a hand truck that is constructed to provide several unique mechanical advantages over conventional hand trucks or dollies, namely less physical effort to tilt the hand truck from a vertical orientation to an inclined orientation to maneuver a load supported thereon and also less physical effort to move the hand truck over obstacles, such as curbs, stairs, bumps, and potholes.
2. Description of Related Art
A hand truck, commonly referred to as a dolly, is used to transport heavy boxes, articles, or other loads. A conventional hand truck typically includes an elongated, tubular body or frame having a handle mounted or formed at an upper end thereof and a load support platform that extends perpendicularly from a lower end thereof. A pair of wheels connected by an axle are usually mounted behind the load support platform at the lower end of the body or frame.
In the use of a conventional hand truck, a user places the hand truck in a rest position, in which the body is substantially vertically oriented so as to be perpendicular to a ground or floor surface. In this position, the user places one or more boxes or other load on the load support platform. To maneuver the load, the user tips the hand truck into an inclined position by tilting the body or frame backwardly relative to the load on the platform to thereby elevate the load such that the body and the load are supported on the wheels. In this position, the load support platform is no longer on the ground and the weight of the load is supported by the body or frame and the wheels. As a result, the user is able to pull or push the load to a desired location.
While a conventional hand truck does aid in the transportation of heavy loads, it does have certain drawbacks. For instance, in order to maneuver a load, the user must tip the hand truck from the rest position where the weight of the load is supported by the load support platform to the inclined orientation where the weight of the load is supported by the body or frame and the wheels. However, the heavier or more bulky the load, the more difficult it is to tilt the hand truck. Further, during the tilting procedure, the user must brace the hand truck at the lower portion thereof to prevent premature horizontal movement of the hand truck.
During tilting, the user must also ensure that the load supported on the support platform is stabilized and tilts backwardly on the body or frame and does not tilt forwardly or laterally relative to the hand truck and thereby fall from a properly seated position on the hand truck. Whenever a center of mass of a load is or becomes spaced beyond a forward or side edge of the support platform, the load will always be tilted away from the body or frame of the hand truck when the hand truck is being tilted to the inclined maneuvering orientation. Therefore, the user must provide sufficient force to retain the load against the body or frame during tilting while again, preventing any premature horizontal motion of the hand truck. Not only can the user be injured trying to physically control a load placed on the support platform, but if the load falls, then it is possible to damage the load being maneuvered. This problem becomes greater when several items are stacked on the support platform for concurrent movement and when large or heavy objects are being handled.
Also, while a conventional hand truck can be very helpful when moving heavy loads across generally planar surfaces, the conventional hand truck cannot easily traverse obstacles, such as stairs and curbs. To maneuver the hand truck over such obstacles, a user essentially has to lift the weight of the load and the hand truck to a position where the axle of the wheels is above the obstacle so that wheels can roll over the obstacle. In other words, with the exception of a rolling contact of the wheels of a conventional hand truck with the risers of stairs and the like, the conventional hand truck does not provide any mechanical assistance when moving a load over an obstacle, such as a stair or curb.
In addition, a conventional hand truck is prone to tipping when it encounters an irregularity in a ground surface, such as a bump or a pothole, often resulting in spilling the item or items being transported. When one wheel of the conventional hand truck encounters the surface irregularity, the body and the load supporting platform, which is perpendicularly mounted thereto, become laterally angled or tilted. As a result, the skewed load support platform causes the load to slide off of the hand truck.
Thus, there remains a need for a hand truck that can be more easily and safely tilted from a rest position to an inclined maneuvering orientation. There also exists a need for a hand truck that can easily traverse obstacles, such as stairs and curbs. Lastly, there is a need for a hand truck that remains stable when it encounters an irregularity in a ground surface, such as a bump or a pothole.